Scar tissue formation is a common response to injury in most tissues of adult mammals and it can significantly impair the integrity and function of afflicted tissues. Regenerative extracellular matrices (ECMs) for tissue repair, comprised of natural biological molecules, can be derived from various cell and tissue sources via acellularization approaches. Embryonic stem (ES) cells are the most primitive stem cells capable of differentiating into all somatic cell types comprising the three germ lineages (ectoderm, endoderm and mesoderm). ES cells spontaneously differentiate in vitro via embryoid body (EB) formation, whereby multi-cellular aggregates formed in suspension recapitulate the molecular microenvironment regulating cell signaling and fate decisions in the pre- gastrulation stages of tissue morphogenesis. We have developed an acellularization technique to yield novel extracellular matrices from ES cells undergoing differentiation via EB formation. The objectives of this proposal are to 1) determine the efficiency of acellularization of EBs with different solvent extraction techniques, 2) quantify the retention of ECM molecules within the resulting acellular material and 3) assess the functional regenerative potential of the ECM derived from EB cells in a murine dermal wound healing model. The completion of these aims will yield new biological information about the composition and function of primitive ECM produced by ES cells during the course of early differentiation. In addition, these studies will examine the regenerative capability of a novel acellular embryonic ECM derived directly from ES cells in an adult injury model. This approach represents a fundamentally new concept for the application of stem cells, and more specifically stem cell-derived materials, to regenerative medicine therapies. Scar tissue formation is a significant problem that results from an inadequate wound healing response to most injuries and many chronic diseases in adult mammalian species. [unreadable] [unreadable] [unreadable]